////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 1993-2021 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if ! defined (octave_lex_h)
#define octave_lex_h 1

#include "octave-config.h"

#include <deque>
#include <list>
#include <set>
#include <stack>

#include "comment-list.h"
#include "filepos.h"
#include "input.h"
#include "symscope.h"
#include "token.h"

namespace octave
{
  class interpreter;

  // Is the given string a keyword?
  extern bool iskeyword (const std::string& s);

  // For communication between the lexer and parser.

  class
  lexical_feedback
  {
  public:

    // Track symbol table information when parsing functions.

    class symbol_table_context
    {
    public:

      symbol_table_context (interpreter& interp)
        : m_interpreter (interp), m_frame_stack () { }

      ~symbol_table_context (void) { clear (); }

      void clear (void);

      bool empty (void) const { return m_frame_stack.empty (); }

      std::size_t size (void) const { return m_frame_stack.size (); }

      void pop (void);

      void push (const symbol_scope& scope)
      {
        m_frame_stack.push_front (scope);
      }

      symbol_scope curr_scope (void) const;
      symbol_scope parent_scope (void) const;

    private:

      interpreter& m_interpreter;

      std::deque<symbol_scope> m_frame_stack;
    };

    // Track nesting of square brackets, curly braces, and parentheses.

    class bbp_nesting_level
    {
    private:

      enum bracket_type
      {
        BRACKET = 1,
        BRACE = 2,
        PAREN = 3,
        ANON_FCN_BODY = 4
      };

    public:

      bbp_nesting_level (void) : m_context () { }

      bbp_nesting_level (const bbp_nesting_level& nl)
        : m_context (nl.m_context)
      { }

      bbp_nesting_level& operator = (const bbp_nesting_level& nl)
      {
        if (&nl != this)
          m_context = nl.m_context;

        return *this;
      }

      ~bbp_nesting_level (void) = default;

      // Alias for clear function.
      void reset (void) { clear (); }

      void bracket (void) { m_context.push (BRACKET); }

      bool is_bracket (void)
      {
        return ! m_context.empty () && m_context.top () == BRACKET;
      }

      void brace (void) { m_context.push (BRACE); }

      bool is_brace (void)
      {
        return ! m_context.empty () && m_context.top () == BRACE;
      }

      void paren (void) { m_context.push (PAREN); }

      bool is_paren (void)
      {
        return ! m_context.empty () && m_context.top () == PAREN;
      }

      void anon_fcn_body (void) { m_context.push (ANON_FCN_BODY); }

      bool is_anon_fcn_body (void)
      {
        return ! m_context.empty () && m_context.top () == ANON_FCN_BODY;
      }

      bool is_bracket_or_brace (void)
      {
        return (! m_context.empty ()
                && (m_context.top () == BRACKET || m_context.top () == BRACE));
      }

      bool none (void) { return m_context.empty (); }

      void remove (void)
      {
        if (! m_context.empty ())
          m_context.pop ();
      }

      void clear (void)
      {
        while (! m_context.empty ())
          m_context.pop ();
      }

    private:

      std::stack<int> m_context;
    };

    class token_cache
    {
    public:

      // Store an "unlimited" number of tokens.

      // Tokens are allocated with new.  Delete them when they are
      // removed from the cache.
      //
      // One of the reasons for using this class instead of std::deque
      // directly is that we can ensure that memory is cleaned up
      // properly.  It's more tedious to do that with deque since the
      // deque destructor and clear method don't call delete on the
      // elements that it stores.  Another reason is that it makes it
      // easier to change the implementation later if needed.

      token_cache (void) : m_buffer () { }

      // No copying!

      token_cache (const token_cache&) = delete;

      token_cache& operator = (const token_cache&) = delete;

      ~token_cache (void) { clear (); }

      void push (token *tok)
      {
        m_buffer.push_front (tok);
      }

      void pop (void)
      {
        if (! empty ())
          {
            delete m_buffer.back ();
            m_buffer.pop_back ();
          }
      }

      // Direct access.
      token * at (std::size_t n)
      {
        return empty () ? nullptr : m_buffer.at (n);
      }

      const token * at (std::size_t n) const
      {
        return empty () ? nullptr : m_buffer.at (n);
      }

      // Most recently pushed.
      token * front (void)
      {
        return empty () ? nullptr : m_buffer.front ();
      }

      const token * front (void) const
      {
        return empty () ? nullptr : m_buffer.front ();
      }

      token * back (void)
      {
        return empty () ? nullptr : m_buffer.back ();
      }

      const token * back (void) const
      {
        return empty () ? nullptr : m_buffer.back ();
      }

      // Number of elements currently in the buffer.
      std::size_t size (void) const { return m_buffer.size (); }

      bool empty (void) const { return m_buffer.empty (); }

      void clear (void)
      {
        while (! empty ())
          pop ();
      }

    private:

      std::deque<token *> m_buffer;
    };

    lexical_feedback (interpreter& interp)
      : m_interpreter (interp),
        m_end_of_input (false),
        m_allow_command_syntax (true),
        m_at_beginning_of_statement (true),
        m_looking_at_anon_fcn_args (false),
        m_looking_at_return_list (false),
        m_looking_at_parameter_list (false),
        m_looking_at_decl_list (false),
        m_looking_at_matrix_or_assign_lhs (false),
        m_looking_for_object_index (false),
        m_looking_at_indirect_ref (false),
        m_arguments_is_keyword (false),
        m_classdef_element_names_are_keywords (false),
        m_parsing_anon_fcn_body (false),
        m_parsing_class_method (false),
        m_parsing_classdef (false),
        m_parsing_classdef_decl (false),
        m_parsing_classdef_superclass (false),
        m_maybe_classdef_get_set_method (false),
        m_parsing_classdef_get_method (false),
        m_parsing_classdef_set_method (false),
        m_quote_is_transpose (false),
        m_force_script (false),
        m_reading_fcn_file (false),
        m_reading_script_file (false),
        m_reading_classdef_file (false),
        m_buffer_function_text (false),
        m_bracketflag (0),
        m_braceflag (0),
        m_looping (0),
        m_defining_func (0),
        m_looking_at_function_handle (0),
        m_block_comment_nesting_level (0),
        m_command_arg_paren_count (0),
        m_token_count (0),
        m_filepos (1, 1),
        m_tok_beg (),
        m_tok_end (),
        m_string_text (),
        m_current_input_line (),
        m_comment_text (),
        m_help_text (),
        m_function_text (),
        m_fcn_file_name (),
        m_fcn_file_full_name (),
        m_dir_name (),
        m_package_name (),
        m_looking_at_object_index (),
        m_parsed_function_name (),
        m_symtab_context (interp),
        m_nesting_level (),
        m_tokens ()
    {
      init ();
    }

    // No copying!

    lexical_feedback (const lexical_feedback&) = delete;

    lexical_feedback& operator = (const lexical_feedback&) = delete;

    ~lexical_feedback (void);

    void init (void);

    void reset (void);

    int previous_token_value (void) const;

    bool previous_token_value_is (int tok_val) const;

    void mark_previous_token_trailing_space (void);

    bool space_follows_previous_token (void) const;

    bool previous_token_is_binop (void) const;

    bool previous_token_is_keyword (void) const;

    bool previous_token_may_be_command (void) const;

    void mark_as_variable (const std::string& nm);
    void mark_as_variables (const std::list<std::string>& lst);

    interpreter& m_interpreter;

    // true means that we have encountered eof on the input stream.
    bool m_end_of_input;

    // true means command syntax is allowed.
    bool m_allow_command_syntax;

    // true means we are at the beginning of a statement, where a
    // command name is possible.
    bool m_at_beginning_of_statement;

    // true means we are parsing an anonymous function argument list.
    bool m_looking_at_anon_fcn_args;

    // true means we're parsing the return list for a function.
    bool m_looking_at_return_list;

    // true means we're parsing the parameter list for a function.
    bool m_looking_at_parameter_list;

    // true means we're parsing a declaration list (global or
    // persistent).
    bool m_looking_at_decl_list;

    // true means we're parsing a matrix or the left hand side of
    // multi-value assignment statement.
    bool m_looking_at_matrix_or_assign_lhs;

    // object index not possible until we've seen something.
    bool m_looking_for_object_index;

    // true means we're looking at an indirect reference to a
    // structure element.
    bool m_looking_at_indirect_ref;

    // true means arguments is handled as keyword.
    bool m_arguments_is_keyword;

    // true means "properties", "methods", "events", and "enumeration"
    // are treated like keywords.
    bool m_classdef_element_names_are_keywords;

    // true means we are parsing the body of an anonymous function.
    bool m_parsing_anon_fcn_body;

    // true means we are parsing a class method in function or classdef file.
    bool m_parsing_class_method;

    // true means we are parsing a classdef file
    bool m_parsing_classdef;

    // true means we are parsing the initial classdef declaration
    // portion of classdef file, from the "classdef" token through the
    // optional list of superclasses.
    bool m_parsing_classdef_decl;

    // true means we are parsing the superclass part of a classdef
    // declaration.
    bool m_parsing_classdef_superclass;

    // true means we are parsing a class method declaration line in a
    // classdef file and can accept a property get or set method name.
    // for example, "get.propertyname" is recognized as a function name.
    bool m_maybe_classdef_get_set_method;

    // TRUE means we are parsing a classdef get.method.
    bool m_parsing_classdef_get_method;

    // TRUE means we are parsing a classdef set.method.
    bool m_parsing_classdef_set_method;

    // return transpose or start a string?
    bool m_quote_is_transpose;

    // TRUE means treat the current file as a script even if the first
    // token is "function" or "classdef".
    bool m_force_script;

    // TRUE means we're parsing a function file.
    bool m_reading_fcn_file;

    // TRUE means we're parsing a script file.
    bool m_reading_script_file;

    // TRUE means we're parsing a classdef file.
    bool m_reading_classdef_file;

    // TRUE means we should store the text of the function we are
    // parsing.
    bool m_buffer_function_text;

    // square bracket level count.
    int m_bracketflag;

    // curly brace level count.
    int m_braceflag;

    // true means we're in the middle of defining a loop.
    int m_looping;

    // nonzero means we're in the middle of defining a function.
    int m_defining_func;

    // nonzero means we are parsing a function handle.
    int m_looking_at_function_handle;

    // nestng level for block comments.
    int m_block_comment_nesting_level;

    // Parenthesis count for command argument parsing.
    int m_command_arg_paren_count;

    // Count of tokens recognized by this lexer since initialized or
    // since the last reset.
    std::size_t m_token_count;

    // The current position in the file (line and column).
    filepos m_filepos;

    // The positions of the beginning and end of the current token after
    // calling update_token_positions.  Also used apart from
    // update_token_positions to handle the beginning and end of
    // character strings.
    filepos m_tok_beg;
    filepos m_tok_end;

    // The current character string text.
    std::string m_string_text;

    // The current line of input.
    std::string m_current_input_line;

    // The current comment text.
    std::string m_comment_text;

    // The current help text.
    std::string m_help_text;

    // The text of functions entered on the command line.
    std::string m_function_text;

    // Simple name of function file we are reading.
    std::string m_fcn_file_name;

    // Full name of file we are reading.
    std::string m_fcn_file_full_name;

    // Directory name where this file was found.  May be relative.
    std::string m_dir_name;

    // Name of +package containing this file, if any.
    std::string m_package_name;

    // if the front of the list is true, the closest paren, brace, or
    // bracket nesting is an index for an object.
    std::list<bool> m_looking_at_object_index;

    // if the top of the stack is true, then we've already seen the name
    // of the current function.  should only matter if
    // current_function_level > 0
    std::stack<bool> m_parsed_function_name;

    // Track current symbol table scope and context.
    symbol_table_context m_symtab_context;

    // is the closest nesting level a square bracket, squiggly brace,
    // a paren, or an anonymous function body?
    bbp_nesting_level m_nesting_level;

    // Tokens generated by the lexer.
    token_cache m_tokens;
  };

  // base_lexer inherits from lexical_feedback because we will
  // eventually have several different constructors and it is easier to
  // initialize if everything is grouped in a parent class rather than
  // listing all the members in the base_lexer class.

  class
  base_lexer : public lexical_feedback
  {
  public:

    // Handle buffering of input for lexer.

    class input_buffer
    {
    public:

      input_buffer (void)
        : m_buffer (), m_offset (0), m_chars_left (0), m_eof (false)
      { }

      void fill (const std::string& input, bool eof_arg);

      // Copy at most max_size characters to buf.
      int copy_chunk (char *buf, std::size_t max_size, bool by_lines = false);

      bool empty (void) const { return m_chars_left == 0; }

      bool at_eof (void) const { return m_eof; }

    private:

      std::string m_buffer;
      std::size_t m_offset;
      std::size_t m_chars_left;
      bool m_eof;
    };

    // Collect comment text.

    class
    comment_buffer
    {
    public:

      comment_buffer (void) : m_comment_list (nullptr) { }

      ~comment_buffer (void) { delete m_comment_list; }

      void append (const std::string& s, comment_elt::comment_type t)
      {
        if (! m_comment_list)
          m_comment_list = new comment_list ();

        m_comment_list->append (s, t);
      }

      // Caller is expected to delete the returned value.

      comment_list * get_comment (void)
      {
        comment_list *retval = m_comment_list;

        m_comment_list = nullptr;

        return retval;
      }

      void reset (void)
      {
        delete m_comment_list;

        m_comment_list = nullptr;
      }

    private:

      comment_list *m_comment_list;
    };

    base_lexer (interpreter& interp)
      : lexical_feedback (interp), m_scanner (nullptr), m_input_buf (),
        m_comment_buf ()
    {
      init ();
    }

    // No copying!

    base_lexer (const base_lexer&) = delete;

    base_lexer& operator = (const base_lexer&) = delete;

    virtual ~base_lexer (void);

    void init (void);

    virtual bool is_push_lexer (void) const { return false; }

    virtual void reset (void);

    void prep_for_file (void);

    void begin_string (int state);

    virtual int fill_flex_buffer (char *buf, unsigned int max_size) = 0;

    bool at_end_of_buffer (void) const { return m_input_buf.empty (); }

    bool at_end_of_file (void) const { return m_input_buf.at_eof (); }

    int handle_end_of_input (void);

    char * flex_yytext (void);

    int flex_yyleng (void);

    int text_yyinput (void);

    void xunput (char c, char *buf);

    void xunput (char c);

    void update_token_positions (int tok_len);

    bool looking_at_space (void);

    bool inside_any_object_index (void);

    int make_keyword_token (const std::string& s);

    bool fq_identifier_contains_keyword (const std::string& s);

    bool whitespace_is_significant (void);

    // We only provide specializations with base equal to 2, 10, or 16.
    template <int base>
    int handle_number (void);

    void handle_continuation (void);

    void finish_comment (comment_elt::comment_type typ);

    comment_list * get_comment (void) { return m_comment_buf.get_comment (); }

    int handle_close_bracket (int bracket_type);

    bool looks_like_command_arg (void);

    int handle_superclass_identifier (void);

    int handle_meta_identifier (void);

    int handle_fq_identifier (void);

    int handle_identifier (void);

    void maybe_warn_separator_insert (char sep);

    void warn_single_quote_string (void);

    void warn_language_extension (const std::string& msg);

    void maybe_warn_language_extension_comment (char c);

    void warn_language_extension_continuation (void);

    void warn_language_extension_operator (const std::string& op);

    void push_token (token *);

    token * current_token (void);

    std::size_t pending_token_count (void) const;

    void display_token (int tok);

    void fatal_error (const char *msg);

    bool debug_flag (void) const;

    bool display_tokens (void) const;

    void increment_token_count (void);

    void lexer_debug (const char *pattern);

    // Internal state of the flex-generated lexer.
    void *m_scanner;

    // Object that reads and buffers input.
    input_buffer m_input_buf;

    // Object that collects comment text.
    comment_buffer m_comment_buf;

    virtual std::string input_source (void) const { return "unknown"; }

    virtual bool input_from_terminal (void) const { return false; }

    virtual bool input_from_file (void) const { return false; }

    virtual bool input_from_eval_string (void) const { return false; }

    bool input_from_tmp_history_file (void);

    void push_start_state (int state);

    void pop_start_state (void);

    void clear_start_state (void);

    int start_state (void) const { return start_state_stack.top (); }

    void display_start_state (void) const;

    bool maybe_unput_comma_before_unary_op (int tok);

    int handle_op (int tok, bool bos = false, bool compat = true);

    int finish_command_arg (void);

    int handle_token (int tok, token *tok_val = nullptr);

    int count_token (int tok);

    int count_token_internal (int tok);

    int show_token (int tok);

  protected:

    std::stack<int> start_state_stack;
  };

  class
  lexer : public base_lexer
  {
  public:

    lexer (interpreter& interp)
      : base_lexer (interp), m_reader (interp), m_initial_input (true)
    { }

    lexer (FILE *file, interpreter& interp)
      : base_lexer (interp), m_reader (interp, file), m_initial_input (true)
    { }

    lexer (FILE *file, interpreter& interp, const std::string& encoding)
      : base_lexer (interp), m_reader (interp, file, encoding), m_initial_input (true)
    { }

    lexer (const std::string& eval_string, interpreter& interp)
      : base_lexer (interp), m_reader (interp, eval_string),
        m_initial_input (true)
    { }

    // No copying!

    lexer (const lexer&) = delete;

    lexer& operator = (const lexer&) = delete;

    void reset (void)
    {
      m_initial_input = true;

      base_lexer::reset ();
    }

    std::string input_source (void) const
    {
      return m_reader.input_source ();
    }

    bool input_from_terminal (void) const
    {
      return m_reader.input_from_terminal ();
    }

    bool input_from_file (void) const
    {
      return m_reader.input_from_file ();
    }

    bool input_from_eval_string (void) const
    {
      return m_reader.input_from_eval_string ();
    }

    int fill_flex_buffer (char *buf, unsigned int max_size);

    input_reader m_reader;

    // TRUE means we are filling the input buffer for the first time.
    // Otherwise, we are requesting more input to complete the parse
    // and, if printing a prompt, should use the secondary prompt
    // string.

    bool m_initial_input;
  };

  template <> int base_lexer::handle_number<2> ();
  template <> int base_lexer::handle_number<10> ();
  template <> int base_lexer::handle_number<16> ();

  class
  push_lexer : public base_lexer
  {
  public:

    push_lexer (interpreter& interp)
      : base_lexer (interp)
    {
      append_input ("", false);
    }

    push_lexer (const std::string& input, interpreter& interp)
      : base_lexer (interp)
    {
      append_input (input, false);
    }

    push_lexer (bool eof, interpreter& interp)
      : base_lexer (interp)
    {
      append_input ("", eof);
    }

    push_lexer (const std::string& input, bool eof, interpreter& interp)
      : base_lexer (interp)
    {
      append_input (input, eof);
    }

    // No copying!

    push_lexer (const push_lexer&) = delete;

    push_lexer& operator = (const push_lexer&) = delete;

    bool is_push_lexer (void) const { return true; }

    void append_input (const std::string& input, bool eof);

    std::string input_source (void) const { return "push buffer"; }

    int fill_flex_buffer (char *buf, unsigned int max_size);
  };
}

#endif
